Sustainable Heritage Conservation Based on Spatial Evolution and Formation Mechanism of Jiangnan Canal Heritage Settlements Based on Landscape Stratigraphy

Canal heritage settlements in the Jiangnan water-network region constitute a built-environment legacy of sustained, long-term human–water co-adaptation, yet their traditional morphologies and spatial fabrics are undergoing rapid restructuring amid accelerated industrialization and urbanization. Existing analytical approaches remain largely confined to two-dimensional buffer-zone analysis and planar kernel-density estimation, which cannot distinguish whether contact relationships among historical layers represent conformable contacts or angular unconformities, and have failed to translate geological stratigraphic succession into an operational framework for built heritage conservation. Drawing on landscape stratigraphy theory, this study converts historical layering, path dependency, and spatial inheritance into quantifiable GIS indicators, employing an extrusion index, a path-dependency index, a Gaussian residual field model, and Geodetector factor-interaction analysis to interrogate spatial evolution mechanisms. Most settlements exhibit stable stratigraphic layering, while a subset display angular unconformity linked to institutional displacement events and others demonstrate structural wedging toward canal frontages driven by commercial densification. Commercial points of interest retain the strongest clustering lock-in on historical waterway networks, while transportation points of interest remain linearly constrained along the historical canal corridor. Archaeological remnants remain significantly spatially coupled with contemporary land-use patterns through residual field effects even after abandonment or functional weakening. Water-network density and historical period exhibit enhanced synergistic effects on settlement spatial differentiation. These findings indicate that the spatial evolution of canal heritage settlements follows a stratigraphic logic, in which the vertical embeddedness of historical infrastructure is associated with the horizontal elasticity of contemporary spatial responses. The proposed metrics furnish replicable quantitative tools for heritage zoning and sustainable conservation planning.